diff --git a/interface.lisp b/interface.lisp
index a1a79e2d86820c1b3461908801f5b6686ba93b0c..411ab5472a0fbc4e0ad2c1c1a0dd98eebe8f9b2e 100644
--- a/interface.lisp
+++ b/interface.lisp
@@ -77,6 +77,7 @@
    #:system-maintainer
    #:system-license
    #:system-licence
+   #:system-version
    #:system-source-file
    #:system-source-directory
    #:system-relative-pathname
diff --git a/system.lisp b/system.lisp
index cdfc57231b421b53a24f1af1e263680450f1311a..6450df2be45d945a566030b99e8874779dcb9cf5 100644
--- a/system.lisp
+++ b/system.lisp
@@ -9,6 +9,7 @@
    #:system-source-file #:system-source-directory #:system-relative-pathname
    #:system-description #:system-long-description
    #:system-author #:system-maintainer #:system-licence #:system-license
+   #:system-version
    #:definition-dependency-list #:definition-dependency-set #:system-defsystem-depends-on
    #:system-depends-on #:system-weakly-depends-on
    #:component-build-pathname #:build-pathname
@@ -72,21 +73,22 @@ NB: This interface is subject to change. Please contact ASDF maintainers if you
 a SYSTEM is redefined and its class is modified."))
 
   (defclass system (module proto-system)
-    ;; Backward-compatibility: inherit from module. ASDF4: only inherit from parent-component.
-    (;; {,long-}description is now inherited from component, but we add the legacy accessors
-     (description :accessor system-description)
-     (long-description :accessor system-long-description)
-     (author :accessor system-author :initarg :author :initform nil)
-     (maintainer :accessor system-maintainer :initarg :maintainer :initform nil)
-     (licence :accessor system-licence :initarg :licence
-              :accessor system-license :initarg :license :initform nil)
-     (homepage :accessor system-homepage :initarg :homepage :initform nil)
-     (bug-tracker :accessor system-bug-tracker :initarg :bug-tracker :initform nil)
-     (mailto :accessor system-mailto :initarg :mailto :initform nil)
-     (long-name :accessor system-long-name :initarg :long-name :initform nil)
+    ((long-name :writer (setf system-long-name) :initarg :long-name :initform nil)
+     ;; Backward-compatibility: inherit from module. ASDF4: only inherit from parent-component.
+     ;; {,long-}description is now inherited from component, but we add the legacy accessors
+     (description :writer (setf system-description))
+     (long-description :writer (setf system-long-description))
+     (author :writer (setf system-author) :initarg :author :initform nil)
+     (maintainer :writer (setf system-maintainer) :initarg :maintainer :initform nil)
+     (mailto :writer (setf system-mailto) :initarg :mailto :initform nil)
+     (homepage :writer (setf system-homepage) :initarg :homepage :initform nil)
      ;; Conventions for this slot aren't clear yet as of ASDF 2.27, but whenever they are, they will be enforced.
      ;; I'm introducing the slot before the conventions are set for maximum compatibility.
-     (source-control :accessor system-source-control :initarg :source-control :initform nil)
+     (source-control :writer (setf system-source-control) :initarg :source-control :initform nil)
+     (licence :writer (setf system-licence) :initarg :licence
+	      :writer (setf system-license) :initarg :license
+	      :initform nil)
+     (bug-tracker :writer (setf system-bug-tracker) :initarg :bug-tracker :initform nil)
      (builtin-system-p :accessor builtin-system-p :initform nil :initarg :builtin-system-p)
      (build-pathname
       :initform nil :initarg :build-pathname :accessor component-build-pathname)
@@ -162,6 +164,35 @@ NB: The onus is unhappily on the user to avoid clashes."
     (frob-substrings (coerce-name name) '("/" ":" "\\") "--")))
 
 
+;;; System virtual slot readers, recursing to the primary system if needed.
+(with-upgradability ()
+  (defvar *system-virtual-slots* '(long-name description long-decsription
+				   author maintainer mailto
+				   homepage source-control
+				   licence version bug-tracker)
+    "The list of system virtual slot names.")
+  (defun system-virtual-slot-value (system slot-name)
+    "Return SYSTEM's virtual SLOT-NAME value.
+If SYSTEM's SLOT-NAME value is NIL and SYSTEM is a secondary system, look in
+the primary one."
+    (or (slot-value system slot-name)
+	(unless (primary-system-p system)
+	  (slot-value (find-system (primary-system-name system))
+		      slot-name))))
+  (defmacro define-system-virtual-slot-reader (slot-name)
+    `(defun* ,(intern (concatenate 'string (string :system-)
+				   (string slot-name)))
+	 (system)
+       (system-virtual-slot-value system ',slot-name)))
+  (defmacro define-system-virtual-slot-readers ()
+    `(progn ,@(mapcar (lambda (slot-name)
+			`(define-system-virtual-slot-reader ,slot-name))
+		*system-virtual-slots*)))
+  (define-system-virtual-slot-readers)
+  (defun system-license (system)
+    (system-virtual-slot-value system 'licence)))
+
+
 ;;;; Pathnames
 
 (with-upgradability ()